146 



THE VOYAGE OF H.M.S. CHALLENGER. 



female.^ The umbrella is larger than usual in the genus, reaching on an average about one- 

 third up the arms ; the huccal membrane has seven not very prominent points, and there is 

 a spermatic 2xtd as usual (fig. 3) ; the outer Up is very thin, the inner thick and papillate. 



The Tentacle is about as long as the body, stout, indistinctly three-sided, and 

 tapering. The club (fig. 7) is short and but little expanded, with a narrow protective 

 membrane on its outer side ; the sucker-bearing area is, as it were, undermined on its 

 inner aspect by a deep groove or fissure, and internally to this again is a broad fin 

 which reaches down the tentacle for a distance exceeding half the length of the club. 

 There are three suckers much longer than the rest, whereof the middle one is the largest 

 and the proximal the next, placed on stout peduncles arising in deep depressions ; 

 towards the outer side of the club is a series of about four medium-sized suckers, and 

 beyond these again one or two series of minute ones. The horny rings appear smooth 

 under a powerful hand-lens, though the microscope reveals a fine irregular denticulation. 



The Surface is smooth in general, but there are a few irregular papillae in the 

 ventro-lateral region. 



The Colour is a dull grey, with indications of annular markings on the back disposed 

 in the form of a cross (fig. 1). 



The Shell (figs. 4, 5) has a rhomboidal outline, with rounded anterior and lateral 

 angles ; the chitinous m.argin is narrow, widest behind, where it forms a flat, acute- 

 angled plate, the posterior extremity of the shell ; it covers entirely, however, the 

 dorsal surface, which is slightly raised mesially and marked by a number of faint striae 

 radiating from the posterior end. The ventral surface is much elevated on either side 

 of a median groove ; the last loculus is bounded by a wavy line, and deeply emarginate 

 in the middle ; it has an index of 22. The inner cone is represented only by a narrow 

 rib reaching halfway along each posterior side of the shell and meeting its fellow in a 

 rounded angle behind, from which a number of radiating calcareous streaks pass outwards 

 into the horny termination. 



Dimensions. 



Length, total. 



End of body to mantle-margin, 



End of body to eye, 



Breadtli of body (excluding fin), 



Breadth of head, . 



Eye to edge of umbrella, . 



Breadth of fin, 



Diameter of largest sucker on sessile arm, 



Diameter of largest sucker on tentacle, 



Length of shell, . 



Breadth of shell, . 



Thickness of shell. 



110 mm. 



52 „ 



60 „ 



32 „ 



32 „ 



18 „ 



8 „ 



1 ,, 



2 „ 

 45 „ 

 24 „ 



8 „ 



Appelldf records that he found no trace of the formation of the hectocotylus in the male examined by him. 



